Casting metal



UNITED STATES PATENT OFFICE.

JAMES DUFF, OF PEORIA, ILLINOIS.

CASTING METAL.

SPECIFICATION forming part of Letters Patent No. 229,308, dated June 29,1880. Application filed October 16, 1879.

To all whom it may concern:

Be it known that I, JAMES DUFF, of the city and county of Peoria, andState of Illinois, have invented a new and useful Improvement in CastingMetals; and I do hereby declare that the following is a full, clear, andexact description of the same.

To get rid of blow-holes and points of weakness caused by particles ofoxide has long been a desideratum in the working of iron and steel. Asthe cause of the former I have discovered that a part of the smallquantities of oxygen which remain in and are taken up by the hot ironand steel and their alloys, as they have heretofore been manufacturedand east, leaves its union with the metals during the casting processand unites with the carbon contained in the metal, and forms smallquantities of carbonic-oxide or other gas, which is imprisoned by thecooling metal, thereby making it porous when cast and destroying itssolidity and strength. The gas-cells or blow-holes which are thus formedin the ingots or castings can seldom be entirely worked out, so as tomake the metal as strong, homogeneous, and solid as if they had neverexisted. Otherjparts of the small quantities of oxygen so retained ortaken up by the metal in its molten state, or by substances mixed orcombined with the metal, remain in the metal in the form of metallic andother oxides, and are not and cannot be removed entirely by forging orany process of manufacture now in use, being simply flattened orlengthened out by such treatment to form lines of weakness. Such beingthe character of the ordinary merchantable malleable iron and steel, itrenders them less homogeneous, more difficult to cast and manufacture,and less solid and strong when cast and manufactured, and, Ibelieve,more liable to further and future oxidation. These objections do notapply to such an extent to ordinary cast-iron, for the reason that thepresence of silicon in large quantities permits solidity to be morefrequently obtained, and from which fact cast-iron is in practicesuccessfully cast into form direct. These objections apply to steel andmalleable iron, however, to such an extent as to practically precludethe casting of these metals into form direct, necessitating, instead,the casting into ingots first, and then My complete process consists infirst deoxi- I dizing the molten metal beneath a surface which shallprotect it from the air, and then, while in this melted condition,pouring or castin g the metal into form in an atmosphere containin g nooxygen.

In the deoxidizin g process any ordinary crucible steel-furnace may beused and the metal melted, as is ordinarily done in such furnaces.

The deoxidizing is accomplished by putting the deoxidizing compoundhereinafter described into the crucible with the metal. This may be donebefore melting or at any stage of the melting process. I prefer puttingit in before and in the bottom of the crucible, or the melted metal maybe poured upon the mixture. The metal should be retained in a liquidstate, after the compound is put in, until the metallic oxide and otheroxides existing in the metal are entirely absorbed by the deoxidizingagent and have had time to rise to.

the surface and be liberated from theiron or steel. This will beindicated by the ebullition ceasing and not recurring when the crucibleis shaken or moved. The lid of the crucible should be kept closed asmuch as possible from the beginning of the melting until the metal isready to be poured, in order to keep air and carbonic-acid andcarbonic-oxide, or other oxidizing gases, from coming in contact withthe heated metal, and the slag hereinafter described should be used asdirected.

If the molds are of such a size and shape as to make it probable thatthe metal will not readily flow into all the parts it may be heatedseveral degrees hotter than the melting-point just before pouringwithout injury to the metal, as it is never exposed to oxidation duringthe heated state in casting by my process.

The deoxidizing compound which I use is and other oxidizing gases.

composed of the following ingredients in the following proportions oxideof silicon, (clean sand,) five ounces; carbon, (pulverized charcoal,)two ounces; pulverized iron, (fine iron turnings,) thirty ounces. Thisshould be well mixed together and placed in the bottom of the crucible,and will ordinarily be the proper quantity for a melt consisting ofsixty pounds of ordinary scrap-steel comparatively free from coatings ofrust and ten pounds of wroughtiron reasonably free from exterior rust oroxide. A greater proportion of wrought-iron, as compared with the steel,and a greater quantity of rust on the iron and steel,will make a greaterquantity of the compound advisable. If an excess of the compound isused-that is, if more silicon is disengaged by the decomposition of thecompound than can be taken up by the oxygen of the metals-it may unitewith the metal. A small quantity of silicon is not usually consideredinjurious to the metal. This depends somewhat upon the purpose for whichthe metal is to be used.

By my process of casting the presence of silicon and ofmanganese andsome other alloys of a like nature, if injurious at all, is renderedless injurious than when the metals are cast by other processes. It isnot so much the presence of these substances that injures the iron orsteel as the presence of the oxides of them imprisoned in the coolingmetal before they have time to rise to the surface. If the compound isnot used in excess the silicon will not unite with the iron or steel,but will ounces; carbon, (pulverized charcoal,) one and one-half ounce;oxide of manganese, (black,) two ounces; pulverized iron, (fine ironturnings,) twenty ounces. Mix these well together. Use this quantity asa substitute for the foregoing quantity of the first compound, and usein the same way.

, Steel and iron containing a considerable per cent. of carbon, silicon,manganese, or other (leoxidizin g agent, may be deoxidized bymaintaining it in its molten state while protected by the slaghereinafter described, or other similar slag, and as much as possible bythe lid of the crucible.

I place upon the metal in the crucible a compound composed of one poundof aluminous clay and one or two ounces of lime, as it may be desired tohave the slag more or less liquid. The larger portion of lime makes themore liquid slag. This compound will melt and form a complete protectionto the metal from contact with the air, carbonic acid, Small globules ofthe metal'will be thrown into the slag, and by the ebullition be carriedto the top of the slag, and for this reason it is desirable to keep thecover of the crucible closed as much as possi- 1016 during the process.This slag will remain After thorough deoxidation, as before described,the metal is carried to the pouringchamber, conveniently situated nearthe meltin g-furnace.

The pouring-chamber is constructed as described in a patent issued to mehearing date the 28th day of May, A.D. 1878; butother pouring-chambersmay be constructed to accomplish the same purpose. The metal is putintosaid molding-chamber and poured into the molds as described in thatpatent.

Iron and steel should be poured in an atmosphere of nitrogen gas. Anygas that does not contain oxygen, or does not have a direct affinity forthe metal in its heated state to form a salt, may be used. Nitrogen isthe best, according to my present knowledge and experience, it beingodorless, not injurious to the lungs of the workmen, not explosive, andnot injurious to the metal.

Among other gases not containing oxygen which may be successfully usedare hydrogen and carbureted hydrogen. Such gases as chlorine, althoughnot containing oxygen, could not be used on account of their directaffinity for the metal.

Great care must be taken to have the molding-chamber and the gas freefrom dampness and the molds perfectly dry and free from oxide of ironand every other substance that will be decomposed by the heat or heatediron or the carbon in the iron, and give off oxygen. Iron molds must be,and it is better that all molds should be, carefully luted with somesubstance entirely free from oxygen. A mixture of lamp-black and spiritsof turpentine is good.

In defining my invention more clearly, I would state that I do notclaim, broadly, deoxidizing iron or steel by the compositiondescribed,'as I am aware that substantially similar deoxidizing compounds havebeenheretofore employed. 1 am aware also of the English Patent to Bessemer,N 0. 1,292 of 1856, and the United States Patent to Ghubb, No. 65,473,granted June 4, 1867. I therefore do not claim, broadly, casting iron orsteel in an atmosphere containing no oxygen. I do not know, however,that iron and steel have ever been deoxidized and then, while in thesame melted condition in which said deoxidation took place, immediatelypoured or cast in an atmosphere containing no oxygen, and from thesesuccessiveand coacting steps there results the perfect product which hasnot been. heretofore obtained-4. 0., a perfectly dense homogeneouscasting of steel or malleable iron entirely free from holes, particlesof oxide, and lines of weakness, which renders practical the casting ofsuch metals into form direct. That these two steps, practiced under thesame melt, do coact to produce this result is evidenced by the fact thatneither of these steps, conducted separately, can give such result, Forif, leaving out the first step, we pour iron or steel containing more orless oxide in an atmosphere containing no oxygen, the particles of oxidedecompose at the high heat at which these metals are poured and theoxygen of said oxide unites with the carbon in the steel or iron andforms in little globules a gas (carbonic-oxide) which is im prisoned inthe casting, and renders it porous,

notwithstanding the fact that no air or oxygen had access to it duringthe melting and, casting. On the other hand, if the second step ofcasting in an atmosphere containing no oxygen is dispensed with, nomatter how thorough the deoxidation is, if the metal has any

